The sol-gel process, which in the most general sense is based on inorganic polymerization reactions, is considered a unique route for the chemical synthesis of ceramic-containing materials. The process provides a low-temperature route for preparing ceramic materials with excellent homogeneity, a low sintering temperature, low impurity levels, and customizable physical features.
The wide availability of metal alkoxide precursors facilitates preparation of almost any type of ceramic composition, including some phases not achievable through conventional high-temperature processes. By combining various metal alkoxides, unique amorphous networks can be prepared in chemical compositions matching those of almost all metal oxides currently available in powder form. With such a large potential for developing numerous types of ceramic systems, sol-gel science can be utilized in almost any type of ceramics application.
The xe2x80x9c0-3 compositexe2x80x9d concept focuses upon the development of thick sol-gel-derived ceramic composite films. They are deposited from a solution comprised of both macroscopically liquid (sol) and particulate (aggregate) phases. The liquid portion is derived via a relatively conventional sol-gel route toward the preparation of oxide coatings. This sol phase, which contains the reactive alkoxide precursors, subsequently gels and condenses to form a matrix that entraps the particulate phase (1-2). This process is analogous to the fabrication of a brick wall, wherein the sol-gel-derived matrix acts as mortar and the entrapped oxide particles act as bricks (2).
The designation xe2x80x9c0-3xe2x80x9d refers to the connectivity of the elements in each phase; that is, the entrapped particulate phase exhibits no interparticle connectivity while the sol phase exhibits three-dimensional connectivity upon gelation. Thus, 0-3 composites result from a hybrid colloid particle-sol-gel suspension.
Compared to typical sol-gel processes, the 0-3 composite method produces films that (1) are orders of magnitude thicker per coating application, (2) can form with very little or no cracking, and (3) dry into more densely packed films (xerogels). These 0-3 composite films also exhibit substantially lower consolidation temperatures and better substrate adhesion than traditional paste-derived layers. For these reasons, 0-3 composites appear to be promising candidates for developing highly densified thick ceramic films at low temperatures.
Needs exist for a direct-write process for writing electronic components onto low-temperature plastic substrates. That need is addressed by the inventive sol-gel-based 0-3 composite process described in the ongoing specification. The present inventors have achieved surprising results by combining the sol-gel process and the 0-3 composite process.
Sol-gel-derived xe2x80x9c0-3 compositexe2x80x9d ceramics are being developed under the DARPA MICE (Defense Advanced Research Project Agency, Mesoscopic Integrated Conformal Electronics) program for application to electronics components directly written onto low-temperature substrates.
The 0-3 composite materials are prepared from a mixture of liquid-phase and solid-phase constituents, as are the pastes conventionally used to prepare thick-film materials for the electronics industry. When compared with conventional paste materials and processes, however, the new 0-3 composites exhibit several potential advantages, including substantial reductions in (1) processing temperatures, (2) solvent concentrations, and (3) organic post-processing-residual concentrations.
In addition, the rapid removal of solvent during application is compatible with such rapid prototyping methods as laser densification. Preliminary results of the CMS Technetronics, Inc.xe2x80x94Oklahoma State University (OSU) Mesoscopic Integrated Conformal Electronics (MICE) project clearly indicate that 0-3 composites may be deposited onto plastic substrates while still meeting expected performance standards. Therefore, the direct writing of electronics components onto such low temperature substrates as plastic may be achieved using sol-gel-based 0-3 composites. The inventive process is useful for resistors, capacitors, insulators, inductors and conductors.
These and further and other objects and features of the invention are apparent in the disclosure, which includes the above and ongoing written specification and the claims.